CHAPTER V. 



ROTATION OF CROPS. 



The aim of rotations — Results of bare fallow — Effect of green crops, fed on 

 the land or ploughed in — Distinctive characteristics of crops — Dif- 

 ferences in periods of growth, depth of roots, powers of assimilation, 

 and quantity of food demanded — Losses to the land during rotation — 

 Actual loss in an assumed four-course rotation — Probable gain of 

 nitrogen from the atmosphere — Sale of produce other than corn and 

 meat. 



It is by no means impossible to grow the same crop 

 with success year after year on the same land ; ordinary 

 pasture is indeed an example of continuous cropping. 

 The Rothamsted experiments show that excellent crops of 

 wheat, barley, and mangel may be continuously obtained 

 if appropriate manure is annually applied, and the land 

 kept free from weeds. A rotation of crops is resorted to 

 in ordinary practice from the facilities which such a plan 

 affords for cleaning the land, and from the greater economy 

 of manure which results from this practice. One of the 

 principal aims of a rotation is to bring the land from time 

 to time into a condition suitable for growing cereal crops ; 

 this suitable condition consists mainly in the accumula- 

 tion of nitrogenous plant food in the surface soil. 



Bare Fallow. — A bare fallow is one of the oldest modes 

 of preparing soil for wheat. The soil is ploughed, and 

 exposed a whole year to atmospheric influences, and 



